U.S. patent application number 10/117711 was filed with the patent office on 2003-10-09 for electroless deposition method.
Invention is credited to Dixit, Girish, Gandikota, Srinivas, McGuirk, Chris R., Padhi, Deenesh, Ramanathan, Sivakami, Yahalom, Joseph.
Application Number | 20030190812 10/117711 |
Document ID | / |
Family ID | 28674266 |
Filed Date | 2003-10-09 |
United States Patent
Application |
20030190812 |
Kind Code |
A1 |
Padhi, Deenesh ; et
al. |
October 9, 2003 |
Electroless deposition method
Abstract
Methods and apparatus are provided for forming a metal or metal
silicide layer by an electroless deposition technique. In one
aspect, a method is provided for processing a substrate including
depositing an initiation layer on a substrate surface, cleaning the
substrate surface, and depositing a conductive material on the
initiation layer by exposing the initiation layer to an electroless
solution. The method may further comprise etching the substrate
surface with an acidic solution and cleaning the substrate of the
acidic solution prior to depositing the initiation layer. The
initiation layer may be formed by exposing the substrate surface to
a noble metal electroless solution or a borane-containing solution.
The conductive material may be deposited with a borane-containing
reducing agent. The conductive material may be used as a
passivation layer, a barrier layer, a seed layer, or for use in
forming a metal silicide layer.
Inventors: |
Padhi, Deenesh; (San Jose,
CA) ; Yahalom, Joseph; (Emeryville, CA) ;
Ramanathan, Sivakami; (Fremont, CA) ; McGuirk, Chris
R.; (San Jose, CA) ; Gandikota, Srinivas;
(Santa Clara, CA) ; Dixit, Girish; (San Jose,
CA) |
Correspondence
Address: |
Patent Counsel
Applied Materials, Inc.
P.O. Box 450-A
Santa Clara
CA
95052
US
|
Family ID: |
28674266 |
Appl. No.: |
10/117711 |
Filed: |
April 3, 2002 |
Current U.S.
Class: |
438/694 ;
257/E21.165; 257/E21.174; 257/E21.438; 438/692 |
Current CPC
Class: |
C23C 18/1893 20130101;
H01L 21/76874 20130101; H01L 21/76843 20130101; H01L 21/76849
20130101; C23C 18/1651 20130101; H01L 29/665 20130101; H01L
21/28518 20130101; H01L 21/288 20130101; H01L 2221/1089
20130101 |
Class at
Publication: |
438/694 ;
438/692 |
International
Class: |
H01L 021/461 |
Claims
What is claimed is:
1. A method of processing a substrate, comprising: polishing a
substrate surface to expose a first conductive material disposed in
a dielectric material; depositing an initiation layer on the first
conductive material by exposing the substrate surface to a first
electroless solution having a pH of about 7 or less; removing
oxides from the substrate surface; cleaning the substrate surface
of the first electroless solution; and depositing a second
conductive material on the initiation layer by exposing the
initiation layer to a second electroless solution.
2. The method of claim 1, wherein the initiation layer is
continuous or non-continuous.
3. The method of claim 1, wherein the initiation layer is
deposition to a thickness of about 10 .ANG. or less.
4. The method of claim 1, wherein the first electroless solution
comprises a noble metal salt and an inorganic acid.
5. The method of claim 4, wherein the noble metal salt comprises a
salt of palladium, platinum, or combinations thereof.
6. The method of claim 4, wherein the noble metal salt is selected
from the group of a chloride salt, a sulfate salt, sulfamate salt,
or combinations thereof, and the inorganic acid is selected from
the group of hydrochloric acid, sulfuric acid, hydrofluoric acid,
or combinations thereof.
7. The method of claim 4, wherein the noble metal salt has a
concentration of between about 20 parts per million and about 20
grams per liter of the electroless solution.
8. The method of claim 1, wherein the first conductive material is
exposed to the electroless solution for about 300 seconds or
less.
9. The method of claim 4, wherein the first electroless solution
has a pH between about 1 and about 3.
10. The method of claim 1, wherein the first conductive material is
copper, the initiation layer comprises a noble metal selected from
the group of palladium, platinum, and combinations thereof, and the
second conductive material comprises cobalt or a cobalt alloy.
11. A method of processing a substrate, comprising: polishing a
substrate surface to expose copper features formed in a dielectric
material; depositing a noble metal selected from the group of
palladium, platinum, and combinations thereof, selectively on the
exposed copper features by exposing the substrate surface to an
acidic electroless solution containing a noble metal salt, an
inorganic acid, and having a pH between about 1 and about 3;
removing copper oxides from the exposed copper features; cleaning
the substrate surface of the acidic electroless solution; and
depositing cobalt or cobalt alloy on the noble metal with a cobalt
electroless composition.
12. The method of claim 11, wherein the noble metal salt is
selected from the group of a chloride salt, a sulfate salt,
sulfamate salt, or combinations thereof, and the inorganic acid is
selected from the group of hydrochloric acid, sulfuric acid,
hydrofluoric acid, or combinations thereof.
13. The method of claim 11, wherein the noble metal salt has a
concentration of between about 20 parts per million and about 20
grams per liter of the electroless solution.
14. The method of claim 11, wherein the first conductive material
is exposed to the acidic electroless solution for about 300 seconds
or less.
15. The method of claim 11, wherein the acidic electroless solution
has a temperature of between about 15.degree. C. and about
80.degree. C.
16. The method of claim 11, wherein the acidic electroless solution
comprises palladium chloride or palladium sulfate at a
concentration of between about 20 parts per million and about 20
grams per liter in a hydrochloric acid or sulfuric acid aqueous
solution and is applied to the substrate surface for about 300
seconds or less at a temperature between about between about
15.degree. C. and about 80.degree. C.
17. The method of claim 11, wherein the initiation layer is
deposited continuous or non-continuous to a thickness of about 10
.ANG. or less.
18. A method of processing a substrate comprising a dielectric
material and apertures formed therein, the method comprising:
depositing an initiation layer of a conductive material on the
dielectric material and apertures formed therein by a first
electroless solution comprising a noble metal salt, an inorganic
acid, and a pH of about 7 or less; cleaning the substrate surface
of the first electroless solution; and depositing a
cobalt-containing layer on the initiation layer by a second
electroless solution.
19. The method of claim 18, further comprising: depositing a seed
layer on the cobalt-containing layer; and depositing a conductive
material layer on the seed layer.
20. The method of claim 18, further comprising depositing a
conductive material layer on the cobalt-containing layer.
21. The method of claim 18, wherein the noble metal salt comprises
a salt of palladium, platinum, or combinations thereof.
22. The method of claim 18, wherein the noble metal salt is
selected from the group of a chloride salt, a sulfate salt,
sulfamate salt, or combinations thereof, and the inorganic acid is
selected from the group of hydrochloric acid, sulfuric acid,
hydrofluoric acid, or combinations thereof.
23. The method of claim 18, wherein the noble metal salt has a
concentration of between about 20 parts per million and about 20
grams per liter of the electroless solution.
24. The method of claim 18, wherein the first conductive material
is exposed to the electroless solution for about 300 seconds or
less.
25. The method of claim 18, wherein the first electroless solution
has a pH between about 1 and about 3.
26. The method of claim 18, wherein the first electroless solution
comprises palladium chloride or palladium sulfate at a
concentration of between about 20 parts per million and about 20
grams per liter in a hydrochloric acid or sulfuric acid aqueous
solution and is applied to the substrate surface for about 300
seconds or less at a temperature between about 15.degree. C. and
about 80.degree. C.
27. A method of processing a substrate having a conductive
silicon-based material disposed thereon with patterned apertures
formed therein, the method comprising: depositing an initiation
layer on the substrate surface by a first electroless solution
comprising a noble metal salt, an inorganic acid, and a pH of about
7 or less; cleaning the substrate surface of the first electroless
solution; depositing a first metal material on the initiation layer
by exposing the initiation layer to a second electroless solution;
and forming a metal silicide layer by reacting the conductive
silicon-based material and the first metal layer using one or more
annealing processes.
28. The method of claim 27, further comprising depositing a second
metal layer of the metal silicide layer.
29. The method of claim 27, wherein the noble metal salt comprises
a salt of palladium, platinum, or combinations thereof.
30. The method of claim 27, wherein the noble metal salt is
selected from the group of a chloride salt, a sulfate salt,
sulfamate salt, or combinations thereof, and the inorganic acid is
selected from the group of hydrochloric acid, sulfuric acid,
hydrofluoric acid, or combinations thereof.
31. The method of claim 27, wherein the noble metal salt has a
concentration of between about 20 parts per million and about 20
grams per liter of the electroless solution.
32. The method of claim 27, wherein the first conductive material
is exposed to the electroless solution for about 300 seconds or
less.
33. The method of claim 27, wherein the first electroless solution
has a pH between about 1 and about 3.
34. The method of claim 27, wherein the initiation layer comprises
a noble metal selected from the group of palladium, platinum, and
combinations thereof, and the first metal layer comprises cobalt or
a cobalt alloy.
35. The method of claim 27, wherein the one or more annealing
processes comprise annealing the substrate at a temperature between
about 300.degree. C. and about 900.degree. C. to form the metal
silicide layer.
36. The method of claim 27, further comprising etching unreacted
first metal after the one or more annealing steps.
37. The method of claim 27, wherein a layer of barrier material is
deposited on the first metal layer prior to depositing the second
metal layer.
38. The method of claim 27, further comprising treating the
substrate surface to remove oxide formation by a hydrofluoric
dipping technique or a plasma etch technique.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to the fabrication of
semiconductor devices and to the apparatus and methods for
deposition, removal, and modification of materials on a
semiconductor substrate.
[0003] 2. Description of the Related Art
[0004] Recent improvements in circuitry of ultra-large scale
integration (ULSI) on semiconductor substrates indicate that future
generations of semiconductor devices will require sub-quarter
micron multi-level metallization. The multilevel interconnects that
lie at the heart of this technology require planarization of
interconnect features formed in high aspect ratio apertures,
including contacts, vias, lines and other features. Reliable
formation of these interconnect features is very important to the
success of ULSI and to the continued effort to increase circuit
density and quality on individual substrates and die as features
decrease below 0.13 .mu.m in size.
[0005] Currently, copper and its alloys have become the metals of
choice for sub-micron interconnect technology because copper has a
lower resistivity than aluminum, (1.7 .mu..OMEGA.-cm compared to
3.1 .mu..OMEGA.-cm for aluminum), a higher current carrying
capacity, and significantly higher electromigration resistance.
These characteristics are important for supporting the higher
current densities experienced at high levels of integration and
increased device speed. Further, copper has a good thermal
conductivity and is available in a highly pure state.
[0006] Electroplating is one process being used to fill high aspect
ratio features on substrates. Electroplating processes typically
require a thin, electrically conductive seed layer to be deposited
on the substrate. Electroplating is accomplished by applying an
electrical current to the seed layer and exposing the substrate to
an electrolytic solution containing metal ions that plate over the
seed layer.
[0007] Electroless deposition is another process used to deposit
conductive materials. Although electroless deposition techniques
have been widely used to deposit conductive metals over
non-conductive printed circuit boards, electroless deposition
techniques have not been extensively used for forming interconnects
in VLSI and ULSI semiconductors. Electroless deposition involves an
auto catalyzed chemical deposition process that does not require an
applied current for a plating reaction to occur. Electroless
deposition typically involves exposing a substrate to a solution by
immersing the substrate in a bath or by spraying the solution over
the substrate.
[0008] However, copper readily forms copper oxide when exposed to
atmospheric conditions or environments outside of processing
equipment and requires a passivation layer to prevent metal oxide
formation. Metal oxides can result in an increase the resistance of
metal layers, become a source of particle problems, and reduce the
reliability of the overall circuit.
[0009] Additionally, metal oxides may also detrimentally affect
subsequent processing. In one example, oxides may interfere with
electroless deposition techniques. Electroless deposition
techniques require a surface capable of electron transfer for
nucleation, i.e., catalyzing, of a conductive material over that
surface, and oxidized surfaces, for example on copper seed layers
and metal barrier layers, cannot sufficiently participate in
electron transfer for effective electroless deposition.
[0010] One solution is to deposit a passivation layer or
encapsulation layer on the metal layer to prevent metal oxide
formation. Cobalt and cobalt alloys have been observed as suitable
materials for passivating copper. Cobalt may also be deposited by
electroless deposition techniques on copper. However, copper does
not satisfactorily catalyze or initiate deposition of materials
from electroless solutions. One solution is to initiate deposition
from an electroless solution by contacting the copper substrate
with a ferrous material that initiates deposition though a galvanic
reaction. However, the process requires a continuous conductive
surface over the substrate surface that may not be possible with
some passivation applications. Another solution is to activate the
copper surface by depositing a catalytic material on the copper
surface. However, deposition of the catalytic material may require
multiple steps or use catalytic colloid compounds. Catalytic
colloid compounds may adhere to dielectric materials and result in
undesired, excessive, and non-selective deposition of the
passivation material on the substrate surface. Non-selective
deposition of passivation material may lead to surface
contamination, unwanted diffusion of conductive materials into
dielectric materials, and even device failure from short circuits
and other device irregularities.
[0011] Therefore, there is a need for a method and composition for
electroless deposition of conductive materials in sub-micron
features in a substrate surface.
SUMMARY OF THE INVENTION
[0012] Embodiments of the invention described herein generally
provide methods and compositions for forming a metal or a metal
silicide layer using an electroless deposition process. In one
aspect, a method is provided for processing a substrate including
polishing a substrate surface to expose a first conductive material
disposed in a dielectric material, depositing an initiation layer
on the first conductive material, cleaning the substrate surface of
the first electroless solution, and depositing a second conductive
material on the initiation layer by exposing the initiation layer
to an electroless solution. The initiation layer may be formed by
exposing the substrate surface to a noble metal electroless
solution. The second conductive material may be deposited as a
passivation layer, a barrier layer, a seed layer, or for use in
forming a metal silicide layer.
[0013] In another aspect, a method is provided for processing a
substrate including polishing a substrate surface to expose a first
conductive material disposed in a dielectric material, etching the
substrate surface with an acidic solution, cleaning the substrate
of the acidic solution, depositing an initiation layer selectively
on the first conductive material by exposing the substrate surface
to a first electroless solution, cleaning the substrate surface of
the first electroless solution, and depositing a second conductive
material on the initiation layer by exposing the initiation layer
to a second electroless solution. The initiation layer may be
formed by exposing the substrate surface to a noble metal
electroless solution. The second conductive material may be
deposited as a passivation layer, a barrier layer, a seed layer, or
for use in forming a metal silicide layer.
[0014] In another aspect, a method is provided for processing a
substrate including polishing a substrate surface to expose a first
conductive material disposed in a dielectric material, exposing the
substrate surface to a solution comprising a boron-containing
reducing agent, forming initiation sites on the exposed first
conductive material, and depositing a second conductive material on
the initiation sites by exposing the substrate surface to an
electroless solution containing a reducing agent. The second
conductive material may be deposited as a passivation layer, a
barrier layer, a seed layer, or for use in forming a metal silicide
layer.
[0015] In another aspect, a method is provided for processing a
substrate including polishing a substrate surface to expose a first
conductive material disposed in a dielectric material and
depositing a second conductive material on the first conductive
metal by exposing the substrate surface to an electroless solution
containing a boron-containing reducing agent. The second conductive
material may be deposited as a passivation layer, a barrier layer,
a seed layer, or for use in forming a metal silicide layer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] So that the manner in which the above recited aspects of the
invention are attained and can be understood in detail, a more
particular description of the invention, briefly summarized above,
may be had by reference to the embodiments thereof which are
illustrated in the appended drawings.
[0017] It is to be noted, however, that the appended drawings
illustrate only typical embodiments of this invention and are
therefore not to be considered limiting of its scope, for the
invention may admit to other equally effective embodiments.
[0018] FIG. 1 is a flow chart illustrating steps undertaken in
depositing conductive layers according to one embodiment of the
invention;
[0019] FIGS. 2A-2C are schematic sectional views of one deposition
process described herein;
[0020] FIGS. 3A-3C are schematic sectional views of one deposition
process described herein; and
[0021] FIG. 4 is a simplified sectional view of a silicide material
used as a contact with a transistor.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0022] Embodiments of the invention described herein provide
methods and apparatus for depositing a conductive material by an
electroless process. One material that may be deposited is cobalt
or cobalt alloys, which may be deposited as a passivation layer, a
barrier layer, a seed layer, or used in the formation of a metal
silicide layer.
[0023] The words and phrases used herein should be given their
ordinary and customary meaning in the art by one skilled in the art
unless otherwise further defined. Electroless deposition is broadly
defined herein as deposition of a conductive material generally
provided as charged ions in a bath over a catalytically active
surface to deposit the conductive material by chemical reduction in
the absence of an external electric current.
[0024] The processes described herein are performed in apparatus
suitable for performing electroless deposition processes. Suitable
apparatus include an Electra.TM. ECP processing platform or
Link.TM. processing platform that are commercially available from
Applied Materials, Inc., located in Santa Clara, Calif. The Electra
Cu.TM. ECP platform, for example, includes an integrated processing
chamber capable of depositing a conductive material by an
electroless process, such as an electroless deposition processing
(EDP) cell, which are commercially available from Applied
Materials, Inc., located in Santa Clara, Calif. The Electra Cu.TM.
ECP platform generally includes one or more electroless deposition
processing (EDP) cells as well as one or more pre-deposition or
post-deposition cell, such as spin-rinse-dry (SRD) cells, etch
chambers, or annealing chambers. The Electra.TM. ECP processing
platform is more fully described in U.S. Pat. No. 6,258,223, issued
on July 10, which is incorporated by reference herein the extent
not inconsistent with the claimed aspects and description herein.
Embodiment of the Link.TM. processing platform are described in
U.S. patent application Ser. No. 09/603,792, filed on Jun. 26,
2000, and in U.S. patent application Ser. No. 09/891,849, filed on
Jun. 25, 2001, which are incorporated by reference herein the
extent not inconsistent with the claimed aspects and description
herein.
[0025] The Electroless Deposition Process
[0026] In one aspect, a conductive material may be deposited as a
passivation layer on exposed conductive materials after a
planarization or material removal process. In one embodiment, the
passivation layer is deposited by the use of an initiation layer
formed by the electroless deposition of a noble metal. In another
embodiment, an initiation layer is formed using a borane-containing
solution to form a metal boride layer. Optionally, an acidic
pre-treatment can be used prior to depositing or forming the
initiation layer. The electroless conductive layer can be deposited
as a barrier layer or a seed layer in a metallization process. In
another aspect, an electroless conductive layer is deposited on a
silicon-containing material and annealed to form a metal silicide
layer. Cobalt and cobalt alloys are examples of compounds that are
deposited by the conductive material electroless deposition
process.
[0027] FIG. 1 is a flow chart illustrating steps undertaken in
depositing conductive layers according to one embodiment of the
invention. A substrate is introduced into the process 100 and
exposed to an acidic pre-clean or etching process to remove at
least a portion of a substrate surface at Step 110. The substrate
surface generally comprises both dielectric materials and
conductive materials. The etched substrate is then rinsed with a
rinsing agent, such as deionized water, at Step 120.
[0028] An initiation layer is then deposited on the substrate
surface at Step 130. The initiation layer may be electroless
deposition of a noble metal on the exposed conductive material of
the substrate surface or may be a metal boride formed from the
exposure of the exposed conductive metal to a borane-containing
solution. The initiation layer generally forms selectively on the
exposed conductive materials.
[0029] The substrate surface is then rinsed with a rinsing agent to
remove the electroless solution or borane-containing solution at
Step 140. A second conductive material is then electroless
deposited on the initiation layer at Step 150. The second
conductive material is generally cobalt or a cobalt alloy. The
second conductive material is selectively deposited on the exposed
initiation layer. The substrate surface is then cleaned using an
ultrasonic or megasonic cleaning process at Step 160.
[0030] The pre-cleaning composition is an acidic solution, such as
an inorganic acid solution. In one aspect, the acidic solution may
comprise between about 0.2 weight percent (wt. %) and about 5 wt. %
of hydrofluoric acid (HF), for example, about 0.5 wt. % of HF acid.
The acid solution may also comprise nitric acid at a concentration
of between about 1 M and about 5 M, for example about 1 M.
Alternatively, the nitric acid solution may comprise a ratio of
nitric acid to water, such as deionized water, at a ratio of about
5:1 and about 1:5.
[0031] The acidic solution may also comprises a composition of
sulfuric acid at a concentration of between about 0.5 vol % and
about 10 vol % of the composition, for example between about 1 vol
% and about 5 vol %, and hydrogen peroxide at a concentration
between about 5 vol % and about 40 vol % of 35% hydrogen peroxide,
for example about 20 vol % concentration of 35% hydrogen
peroxide.
[0032] The pre-cleaning composition is generally applied to the
substrate surface for between about 5 seconds and about 300
seconds, for example, between about 30 seconds and about 60
seconds, at a flow rate between about 50 ml/min and about 2000
ml/min, for example, between about 700 ml/min and about 900 ml/min
including about 750 ml/min, and at a composition temperature
between about 15.degree. C. and about 60.degree. C., such as
between about 20.degree. C. and about 25.degree. C. Alternatively,
a total application of between about 120 ml and about 200 ml of the
pre-cleaning solution may be used to treat the substrate surface.
The pre-cleaning solution may be applied in the same processing
chamber or processing cell as subsequent deposition processes. An
example of the pre-cleaning composition is about 0.5 wt. % of
hydrofluoric acid, which may be applied at a flow rate of about 750
ml for about 60 seconds at a composition temperature between about
20.degree. C. and about 25.degree. C.
[0033] The pre-cleaning solution of Step 110 is applied to remove
or etch a top portion of the exposed dielectric layer, such as
between about 10 .ANG. and about 50 .ANG., which may contain
contaminant conductive materials from a prior processing step. For
example, stray copper ions may contaminant the top portion of a
dielectric material following a chemical mechanical polishing or
planarizing process.
[0034] A rinsing agent, typically deionized water, is then applied
to the substrate surface to remove any remaining pre-cleaning
composition, any etched materials and particles, and any
by-products that may have formed during the pre-cleaning process at
Step 120. The rinsing agent is generally applied to the substrate
surface for between about 5 seconds and about 300 seconds, for
example, between about 30 seconds and about 60 seconds, at a flow
rate between about 50 ml/min and about 2000 ml/min, for example,
between about 700 ml/min and about 900 ml/min including about 750
ml/min, and at a temperature between about 15.degree. C. and about
80.degree. C., such as between about 20.degree. C. and about
25.degree. C. Alternatively, a total application of between about
120 ml and about 200 ml of the rinsing agent may be used to treat
the substrate surface. The rinsing agent may be applied by spraying
method as well as by any other method for cleaning a substrate,
such as by rinsing in an enclosure containing a cleaning solution
or bath. An example of the rinsing agent is deionized water, which
may be applied at a flow rate of about 750 ml for about 60 seconds
at a temperature between about 20.degree. C. and about 25.degree.
C.
[0035] In one embodiment, an initiation layer is formed on the
exposed conductive materials by the electroless deposition of a
noble metal in Step 130. The noble metal is selected from the group
of palladium, platinum, or combinations thereof. The invention
contemplates the use of other noble metals, such as gold, silver,
iridium, rhenium, rhodium, rhenium, ruthenium, osmium, and
combinations thereof. The noble metal is deposited from an
electroless solution containing at least a noble metal salt, and an
inorganic acid. Examples of noble metal salts include palladium
chloride (PdCl.sub.2), palladium sulfate (PdSO.sub.4), palladium
ammonium chloride, and combinations thereof. Examples of inorganic
acids include hydrochloric acid (HCl), sulfuric acid
(H.sub.2SO.sub.4), hydrofluoric acid (HF) and combinations thereof.
Alternatively, inorganic acids, such as carboxylic acids including
acetic acid (CH.sub.3COOH), may be used in the electroless solution
for the initiation layer.
[0036] The noble metal salt may be in the electroless solution at a
concentration between about 20 parts per million (ppm) and about 20
g/liter, such as between about 80 ppm and about 300 ppm, and, for
example, about 120 ppm. The concentration of the metal salt may
also be described as a volume percent with 1 vol % corresponding to
about 40 ppm. For example, 120 ppm of the noble metal salt
correspond to about 3 vol %. The inorganic acid is used to provide
an acidic electroless composition, for example, a pH of about 7 or
less. A pH level between about 1 and about 3 has been observed to
be effective in electroless deposition of the noble metals from the
electroless solution. An acidic solution has also been observed to
be effective in removing or reducing oxides, such as metal oxides
including copper oxides, from the metal or dielectric surface of
the substrate during the electroless deposition process.
[0037] The electroless solution for the initiation layer is
generally applied to the substrate surface for between about 1
second and about 300 seconds, for example, between about 5 seconds
and about 60 seconds, at a composition temperature between about
15.degree. C. and about 80.degree. C., such as between about
20.degree. C. and about 25.degree. C. The electroless solution is
generally provided at a flow rate between about 50 ml/min and about
2000 ml/min, for example, between about 700 ml/min and about 900
ml/min including about 750 ml/min. In one aspect a total
application of about 120 ml and about 200 ml of electroless
solution was provided to deposit the electroless layer. The
electroless solution generally provides for the deposition of a
noble metal to a thickness of about 50 .ANG. or less, such as about
10 .ANG. or less. The initiation layer may be continuous or
discontinuous.
[0038] An example of an electroless composition for depositing the
initiation material includes about 3 vol % (120 ppm) of palladium
chloride and sufficient hydrochloric acid to provide a pH of about
1.5 for the composition, which is applied to the substrate surface
for about 30 seconds at a flow rate of about 750 ml/min at a
composition temperature of about 25.degree. C.
[0039] In another embodiment, the initiation layer is formed by
rinsing or exposing the exposed conductive materials to a
borane-containing composition in Step 130. The borane-containing
composition forms a metal boride layer selectively on the exposed
conductive metals, which are catalytic sites for subsequent
electroless deposition processes.
[0040] The borane-containing composition includes a borane reducing
agent. Suitable borane-containing reducing agents include alkali
metal borohydrides, alkyl amine boranes, and combinations thereof.
Examples of suitable borane-containing reducing agents include
sodium borohydride, dimethylamine borane (DMAB), trimethylamine
borane, and combinations thereof. The borane-containing reducing
agent comprises between about 0.25 grams per liter (g/L) and about
6 g/L, for example, between about 2 g/L and about 4 g/L, of the
boron-containing composition. The borane-containing composition may
additionally include pH adjusting agents to provide a pH of between
about 8 and about 13. Suitable pH adjusting agents include
potassium hydroxide (KOH), sodium hydroxide (NaOH), ammonium
hydroxide, ammonium hydroxide derivatives, such as tetramethyl
ammonium hydroxide, and combinations thereof.
[0041] The conductive material is exposed to the borane-containing
composition between about 30 seconds and about 180 seconds, for
example, between about 60 seconds and about 120 seconds, at a
composition temperature between about 15.degree. C. and about
80.degree. C., such as between about 20.degree. C. and about
25.degree. C. The borane-containing composition may be delivered to
the substrate at a flow rate between about 50 ml/min and about 2000
ml/min, for example, between about 700 ml/min and about 900 ml/min
including about 750 ml/min. In one aspect a total application of
about 120 ml and about 200 ml of the borane-containing composition
was provided to form the initiation layer of a metal boride
compound.
[0042] An example of a borane-containing composition for forming
the layer includes about 4 g/L of dimethylamine borane (DMAB) and
sufficient sodium hydroxide to provide a pH of about 9 for the
composition, which is applied to the substrate surface for about 30
seconds at a flow rate of about 750 ml/min at a composition
temperature of about 25.degree. C.
[0043] A rinsing agent, typically deionized water, is then applied
to the substrate surface to remove any solution used in forming the
initiation layer at Step 140. The rinsing agent is generally
applied to the substrate surface for between about 5 seconds and
about 300 seconds, for example, between about 30 seconds and about
60 seconds, at a flow rate between about 50 ml/min and about 2000
ml/min, for example, between about 700 ml/min and about 900 ml/min
including about 750 ml/min, and at a temperature between about
15.degree. C. and about 80.degree. C., such as between about
20.degree. C. and about 25.degree. C. Alternatively, a total
application of between about 120 ml and about 200 ml of the rinsing
agent may be used to treat the substrate surface. The rinsing agent
may be applied by spraying method as well as by any other method
for cleaning a substrate, such as by rinsing in an enclosure
containing a cleaning solution or bath. An example of the rinsing
agent is deionized water, which may be applied at a flow rate of
about 750 ml for about 60 seconds at a temperature between about
20.degree. C. and about 25.degree. C.
[0044] A metal layer is deposited by an electroless process on the
initiation layer at Step 150. In one aspect, the metal layer
comprises cobalt or a cobalt alloy. Cobalt alloys include
cobalt-tungsten alloy, cobalt-phosphorus alloy, cobalt-tin alloys,
cobalt-boron alloys, including ternary alloys, such as
cobalt-tungsten-phosphorus and cobalt-tungsten-boron. However, the
invention contemplates the use of other materials, including
nickel, tin, titanium, tantalum, tungsten, molybdenum, platinum,
iron, niobium, palladium, platinum, and combinations thereof, and
other alloys including nickel cobalt alloys, doped cobalt and doped
nickel alloys, or nickel iron alloys, to form the metal layer as
described herein.
[0045] In one embodiment, the metal material is deposited from an
electroless solution containing at least a metal salt and a
reducing agent. The electroless solution may further include
additives to improve deposition of the metal. Additives may include
surfactants, complexing agents, pH adjusting agents, or
combinations thereof.
[0046] Suitable metal salts include chlorides, sulfates,
sulfamates, or combinations thereof. An example of a metal salt is
cobalt chloride. The metal salt may be in the electroless solution
at a concentration between about 0.5 g/L and about 30 g/L, such as
between about 2.5 g/L and about 25 g/L.
[0047] Cobalt alloys, such as cobalt-tungsten may be deposited by
adding tungstic acid or tungstate salts including sodium tungstate,
and ammonium tungstate, and combinations thereof for tungsten
deposition. Phosphorus for the cobalt-tungsten-phosphorus
deposition may be form by phosphorus-containing reducing agents,
such as hypophosphite. Cobalt alloys, such as cobalt-tin may be
deposited by adding stannate salts including stannic sulfate,
stannic chloride, and combinations thereof. The additional metals
salts, for example, for tungsten and tin, may be in the electroless
solution at a concentration between about 0.5 g/L and about 30 g/L,
such as between about 2.5 g/L and about 25 g/L.
[0048] Suitable reducing agents include sodium hypophosphite,
hydrazine, formaldehyde, and combinations thereof. The reducing
agents may also include borane-containing reducing agents, such as
dimethylamine borane and sodium borohydride. The reducing agents
have a concentration between about 1 g/L and about 30 g/L of the
electroless solution. For example, hypophosphite may be added to
the electroless between about 15 g/L and about 30 g/L of the
electroless composition.
[0049] Additives include surfactants, such as RE 610, complexing
agents including salts of carboxylic acids, for example, sodium
citrate and sodium succinate, pH adjusting agents including sodium
hydroxide and potassium hydroxide, and combinations thereof. The
additives can be used to control deposition properties of the
electroless solution. For example, stabilizers prevent unwanted
side reactions while complexing agents may limit available ions in
the electroless solution for deposition of the substrate surface.
Additives have a concentration between about 0.01 g/L and about 50
g/L of the electroless solution, such as between about 0.05 g/L and
about 4 g/L, of the electroless solution. An example of an additive
is the surfactant RE 610, which may be added to the electroless
composition at a concentration between about 0.01 g/L and about 5
g/L. Stabilizers, for example, thiourea and glycolic acid, may also
be in the composition at a concentration of about 1 wt. % or less,
such as about 0.01 wt. %.
[0050] Forming the metal layer includes applying the metal
electroless solutions described herein to the substrate surface for
between about 30 seconds and about 180 seconds, for example,
between about 60 seconds and about 120 seconds, at a composition
temperature between about 60.degree. C. and about 90.degree. C.,
such as between about 70.degree. C. and about 80.degree. C. The
electroless solution is generally provided at a flow rate between
about 50 ml/min and about 2000 ml/min, for example, between about
700 ml/min and about 900 ml/min including about 750 ml/min. In one
aspect a total application of between about 120 ml and about 200 ml
of electroless solution was provided to deposit the electroless
layer. The electroless solution generally provides for the
deposition of a metal layer to a thickness of about 500 .ANG. or
less, such as between about 300 .ANG. and about 400 .ANG..
[0051] An example of a cobalt electroless composition for forming
the metal layer includes about 20 g/L of cobalt sulfate, about 50
g/L of sodium citrate, about 20 g/L of sodium hypophosphite, with
sufficient potassium hydroxide to provide a pH of between about 9
and about 11 for the composition, which is applied to the substrate
surface for about 120 seconds at a flow rate of about 750 ml/min at
a composition temperature of about 80.degree. C. A cobalt-tungsten
layer is deposited by the addition of about 10 g/L of sodium
tungstate.
[0052] In an alternative embodiment of the metal deposition
process, the metal material is deposited from an electroless
solution containing at least a metal salt and a borane-containing
reducing agent. Suitable metal salts include chlorides, sulfates,
include chlorides, sulfates, sulfamates, or combinations thereof.
An example of a metal salt is cobalt chloride. The metal salt may
be in the electroless solution at a concentration between about 0.5
g/L and about 30 g/L, such as between about 2.5 g/L and about 25
g/L.
[0053] Cobalt alloys, such as cobalt-tungsten may be deposited by
adding tungstic acid or tungstate salts including sodium tungstate,
and ammonium tungstate, and combinations thereof for tungsten
deposition. Phosphorus for the cobalt-tungsten-phosphorus
deposition may be form by phosphorus-containing reducing agents,
such as hypophosphite. Cobalt alloys, such as cobalt-tin may be
deposited by adding stannate salts including stannic sulfate,
stannic chloride, and combinations thereof. The additional metals
salts, for example, for tungsten and tin, may be in the electroless
solution at a concentration between about 0.5 g/L and about 30 g/L,
such as between about 2.5 g/L and about 25 g/L.
[0054] Suitable borane-containing reducing agents include alkali
metal borohydrides, alkyl amine boranes, and combinations thereof.
Examples of suitable borane-containing reducing agents include
sodium borohydride, dimethylamine borane (DMAB), trimethylamine
borane, and combinations thereof. The borane-containing reducing
agent comprises between about 0.25 grams per liter (g/L) and about
6 g/L, for example, between about 2 g/L and about 4 g/L, of the
boron-containing composition. The presence of borane-containing
reducing agents allow for the formation of cobalt-boron alloys such
as cobalt-tungsten-boron and cobalt-tin-boron among others.
[0055] Additives include surfactants, such as RE 610, complexing
agents including salts of carboxylic acids, for example, sodium
citrate and sodium succinate, and combinations thereof. The
additives can be used to control deposition properties of the
electroless solution. For example, stabilizers prevent unwanted
side reactions while complexing agents may limit available ions in
the electroless solution for deposition of the substrate
surface.
[0056] Additives have a concentration between about 0.01 g/L and
about 50 g/L of the electroless solution, such as between about
0.05 g/L and about 4 g/L, of the electroless solution. An example
of an additive is the surfactant RE 610, which may be added to the
electroless composition at a concentration between about 0.01 g/L
and about 5 g/L. Stabilizers, for example, thiourea and glycolic
acid, may also be in the composition at a concentration of about 1
wt. % or less, such as about 0.01 wt. %.
[0057] The borane-containing composition may additionally include
pH adjusting agents to provide a pH of between about 8 and about
13. Suitable pH adjusting agents include potassium hydroxide (KOH),
sodium hydroxide (NaOH), ammonium hydroxide, ammonium hydroxide
derivatives, such as tetramethyl ammonium hydroxide, and
combinations thereof.
[0058] Forming the metal layer includes applying the metal
electroless solutions described herein to the substrate surface for
between about 30 seconds and about 180 seconds, for example,
between about 60 seconds and about 120 seconds, at a composition
temperature between about 60.degree. C. and about 90.degree. C.,
such as between about 70.degree. C. and about 80.degree. C. The
electroless solution is generally provided at a flow rate between
about 50 ml/min and about 2000 ml/min, for example, between about
700 ml/min and about 900 ml/min including about 750 ml/min. In one
aspect a total application of between about 120 ml and about 200 ml
of electroless solution was provided to deposit the electroless
layer. The electroless solution generally provides for the
deposition of a metal layer to a thickness of about 500 .ANG. or
less, such as between about 300 .ANG. and about 400 .ANG..
[0059] An example of a cobalt electroless composition for forming
the metal layer with a borane-containing reducing agent includes
about 20 g/L of cobalt sulfate, about 50 g/L of sodium citrate,
about 4 g/L of dimetylamineborane, with sufficient potassium
hydroxide to provide a pH of between about 10 and about 12 for the
composition, which is applied to the substrate surface for about
120 seconds at a flow rate of about 750 ml/min at a composition
temperature of about 80.degree. C. A cobalt-tungsten-boron layer is
deposited by the addition of about 10 g/L of sodium tungstate.
[0060] Borane-containing reducing agents in the metal electroless
deposition process are believed to allow electroless deposition on
exposed conductive material without the need for an initiation
layer. When an initiation layer is first deposited on the substrate
surface prior to the metal electroless deposition, the process is
typically performed in two processing chambers. When the metal
electroless deposition process occurs without the initiation layer,
such as with the use of borane-containing reducing agents in the
metal electroless deposition, the electroless process can be
performed in one chamber.
[0061] The substrate surface is then exposed to an ultrasonic or
megasonic cleaning process at Step 160. The cleaning process uses a
cleaning composition includes a dilute hydrochloric acid to provide
a pH between about 1 and about 3 and de-ionized water. The cleaning
composition is generally applied to the substrate surface for
between about 5 seconds and about 300 seconds at a temperature
between about 15.degree. C. and about 80.degree. C.
[0062] Agitation may be provided by ultrasonic or megasonic energy
applied to the substrate support pedestal or substrate surface. For
example, the ultrasonic energy is applied between about 10 and
about 250 Watts, but such as between about 10 and about 100 Watts.
The ultrasonic energy may have a frequency of about 25 kHz to about
200 kHz, for example, greater than about 40 kHz since this is out
of the audible range and contains fewer disruptive harmonics. If
one or more sources of ultrasonic energy are used, then
simultaneous multiple frequencies may be used. The ultrasonic
energy may be applied between about 3 and about 600 seconds, but
longer time periods may be used depending upon the application.
[0063] The acidic cleaning composition and application of
ultrasonic or mega-sonic energy is believed clean any free cobalt
particles, remove any cobalt oxide or reaction by-products, such as
Co(OH).sub.2 formed during deposition. The cleaning solution is
also believed to remove a thin layer of cobalt material, such as
about 20 .ANG. or less, to remove any random growth or lateral
growth of cobalt materials on the substrate surface and over the
exposed conductive materials. The substrate may then be transferred
for additional processing, such as annealing or subsequent
deposition processes.
[0064] Additionally, the method of depositing the material from an
electroless solution, whether the initiation layer or metal layer,
may include applying a bias to a conductive portion of the
substrate structure if available (i.e. a seed layer), such as a DC
bias, during the electroless deposition process. It is believed
that the bias helps to remove trapped hydrogen gas formed in the
catalytic layer during the deposition process.
[0065] The initiation layer and/or metal layer may be annealed
(i.e., heating) at a temperature between about 100.degree. C. to
about 400.degree. C., for example, between about 100.degree. C. to
about 300.degree. C. The anneal may be performed in a vacuum, for
example, at a pressure lower than 1 mTorr. Alternatively, the
anneal may be performed in a gas atmosphere, such as a gas
atmosphere of one or more noble gases (such as Argon, Helium),
nitrogen, hydrogen, and mixtures thereof. In one embodiment, the
anneal is performed for a time period of at least about 1 minute.
In another embodiment, the anneal is performed for a time period of
about 1 to about 10 minutes. The anneal may be conducted by a rapid
thermal anneal process. It is believed that annealing the substrate
promotes adhesion of the electroless deposited material to the
substrate surface and exposed conductive materials, including
barrier layers and seed layers. It is also believe that the anneal
helps remove hydrogen formed in the electroless deposited materials
during the deposition.
[0066] Metallization Deposition Processes
[0067] Embodiments of the processes described herein relate to
depositing metal and metal silicide layers for passivation layers,
barrier layers, seed layers, and metal silicide layers in feature
formation. The following embodiments are provided for illustrative
purposes and should not be construed or interpreted as limiting the
invention described herein.
[0068] Passivation Layer Deposition
[0069] In one aspect, a metal layer is deposited as a passivation
layer on exposed features as shown in FIGS. 2A-2D. In FIG. 2A, a
substrate 200 is provided having a feature 250 formed therein. The
feature 250 is formed by depositing and patterning a photoresist
material by conventional photolithographic and etching techniques
to define a feature opening 240 in one or more dielectric materials
210 and etching the dielectric materials 210 to define the aperture
240. The one or more dielectric materials 210 include, for example,
silicon dioxide, phosphorus-doped silicon glass (PSG),
boron-phosphorus-doped silicon glass (BPSG), silicon carbide,
carbon-doped silicon dioxide, as well as low dielectric constant
materials, including fluoro-silicon glass (FSG), polymers, such as
polymides, and carbon-containing silicon oxides, such as Black
Diamond.TM., available from Applied Materials, Inc. of Santa Clara,
Calif. The invention also contemplates that one or more dielectric
materials 210 may include semiconductive silicon-containing
materials including polysilicon, doped polysilicon, or combinations
thereof, deposited by methods known or unknown in the art.
[0070] A barrier layer 220 is deposited over the dielectric
material. The barrier layer 220 may be deposited to prevent or
inhibit diffusion of subsequently deposited materials into the
underlying substrate or dielectric layers. Suitable barrier layer
materials include refractory metals and refractory metal nitrides
such as tantalum (Ta), tantalum nitride (TaN.sub.x), titanium (Ti),
titanium nitride (TiN.sub.x), tungsten (W), tungsten nitride
(WN.sub.x), cobalt, cobalt alloys such as cobalt-tungsten alloy,
cobalt-phosphorus alloy, cobalt-tin alloys,
cobalt-tungsten-phosphorus, cobalt-tungsten-boron, and combinations
thereof. The barrier layer may be deposited by chemical vapor
deposition (CVD), physical vapor deposition (PVD), electroless
deposition techniques, or molecular beam epitaxy among others. The
barrier layer may also be a multi-layered film deposited
individually or sequentially by the same or by a combination of
techniques, such as a tantalum nitride layer deposited on a
tantalum layer, both layers deposited by a physical vapor
deposition technique.
[0071] The aperture 240 is then filled by the deposition of a
conductive material 230 into the feature. Conductive materials 230
may include, for example, copper or tungsten. The conductive
material 230, may be deposited by chemical vapor deposition (CVD),
physical vapor deposition (PVD), electrochemical deposition
techniques, such as electroplating, or combinations thereof, with
copper, for example, deposited by an electroplating technique.
Optionally, a seed layer (not shown) of a conductive material may
be deposited before the conductive material 230 to nucleate and
enhance the subsequent deposition of the conductive material
230.
[0072] Following deposition of the material in the aperture 240,
the filled aperture may be further processed by planarizing the
substrate surface and a top portion of the aperture to form feature
250, such as by chemical mechanical polishing (CMP). During the
planarization process, portions of the one or more dielectric
materials 210, the barrier layer 220, and the conductive material
230 are removed from the top of the structure leaving a planar
surface having exposed conductive material 245 of the feature 250
in the dielectric materials 210 as shown in FIG. 2A.
[0073] The substrate is then rinsed or cleaned. One rinsing or
cleaning process may include exposing to an acidic pre-clean or
etching composition to remove at least a portion of a substrate
surface as indicated by the dashed line 260 in FIG. 2B prior to a
rinsing step. The pre-cleaning composition may, for example,
include an acidic solution of about 0.5 wt. % of HF acid, which is
applied to the substrate surface for between about 30 seconds and
about 60 seconds at a composition temperature between about
20.degree. C. and about 25.degree. C. The etched substrate is then
rinsed with deionized water to remove any pre-cleaning solution
from the substrate surface.
[0074] An initiation layer 270 is then deposited on the substrate
surface at Step 130. In FIG. 2C, the initiation layer 270 is
deposited by the electroless deposition of a noble metal on the
exposed conductive material of the substrate surface. The
initiation layer 270 is selectively formed on the exposed
conductive materials 245. The initiation layer may be deposited,
for example, by an initiation electroless solution comprising
between about 80 ppm and about 300 ppm palladium chloride
(PdCl.sub.2) and sufficient hydrochloric acid (HCl) to produce a pH
of between about 1 and about 3. The acidity of the initiation
electroless solution is generally provided in sufficient amounts to
be effective in removing or reducing oxides, such as metal oxides
including copper oxides, from the metal or dielectric surface of
the substrate during the electroless deposition process. The
initiation electroless solution is generally applied to the
substrate surface for between about 5 seconds and about 60 seconds
at a solution temperature between about 20.degree. C. and about
25.degree. C., or at conditions sufficient to deposit the
initiation layer to a thickness of about 10 .ANG. or less.
[0075] Alternatively, a boride layer may be formed by exposing the
barrier layer to a composition including a borane-containing
reducing agent, for example, about 4 g/L of dimethylamine borane
(DMAB) and sufficient sodium hydroxide to provide a pH of about 9
for the composition, which is applied to the substrate surface for
about 30 seconds at a composition temperature of about 25.degree.
C. The substrate surface is then rinsed with deionized water to
remove any remaining electroless solution or borane-containing
composition.
[0076] A passivation layer 280 of a metal, such as cobalt or cobalt
alloy, is then deposited on the initiation layer 270 as shown in
FIG. 2D. The passivation layer is deposited from an electroless
technique using an electroless solution containing a metal salt and
a reducing agent. For example, a passivation electroless solution
of between about 2.5 g/L and about 20 g/L, of cobalt chloride and
cobalt sulfate, and between about 15 g/L and about 30 g/L, of
sodium hypophosphite, and sufficient base to provide a pH level of
between about 9 and about 11, may be used to form the passivation
layer. Dimethylamine borane may be used as the reducing agent at a
concentration between about 0.25 g/L and about 6 g/L. The
passivation electroless solution is generally applied to the
substrate surface for between about 5 seconds and about 120 seconds
at a solution temperature between about 20.degree. C. and about
25.degree. C.
[0077] The substrate surface is then cleaned using a cleaning
composition comprising HCl at a pH between about 1 and about 3 for
between about 5 seconds and about 300 seconds at a solution
temperature between about 15.degree. C. and about 80.degree. C.
Ultrasonic energy is applied to the cleaning composition and/or
substrate to improve the cleaning process. The cleaning composition
is generally applied under conditions sufficient to remove about 20
.ANG. or less of the passivation layer.
[0078] Barrier/Seed Layer Deposition
[0079] In one aspect, a seed layer or barrier layer by an
electroless deposition processes described herein in a
metallization process.
[0080] While the following description is for the deposition of a
seed layer by the processes described herein, the invention
contemplates depositing a barrier layer by the electroless process
described herein by exposing a dielectric surface of the substrate
directly to a composition for forming an initiation layer. The
initiation layer will form on the dielectric surface and allow for
the deposition of the metal layer, such as cobalt, thereon. The
initiation layer may form continuously or non-continuously over the
exposed dielectric surface. For example, palladium can be deposited
on the dielectric material for a cobalt barrier deposition. If
cobalt is used a barrier layer material, the seed layer may be a
copper material.
[0081] In one aspect, a seed layer is deposited by the electroless
process described herein in a metallization scheme as shown in
FIGS. 3A-3D. In FIG. 3A, a substrate 300 is provided having an
aperture 320 formed in one or more dielectric materials 310. The
aperture 320 is formed by depositing and patterning a photoresist
material by conventional photolithographic and etching techniques
to define a feature opening in one or more dielectric materials 310
and then etching the dielectric materials 310 to define the
aperture 320.
[0082] The one or more dielectric materials 310 include, for
example, silicon dioxide, phosphorus-doped silicon glass (PSG),
boron-phosphorus-doped silicon glass (BPSG), silicon carbide,
carbon-doped silicon dioxide, as well as low dielectric constant
materials, including fluoro-silicon glass (FSG), polymers, such as
polymides, and carbon-containing silicon oxides, such as Black
Diamond.TM., available from Applied Materials, Inc. of Santa Clara,
Calif. The invention also contemplates that layer 310 may include
semi-conductive silicon-containing materials including polysilicon,
doped polysilicon, or combinations thereof, deposited by methods
known or unknown in the art.
[0083] A barrier layer 330 is deposited in the aperture 320 and
over the dielectric material forming the substrate surface as shown
in FIG. 3B. The barrier layer 330 may be deposited to prevent or
inhibit diffusion of subsequently deposited materials over the
barrier layer 330 into the underlying substrate or dielectric
layers. Suitable barrier layer materials include refractory metals
and refractory metal nitrides such as tantalum (Ta), tantalum
nitride (TaN.sub.x), titanium (Ti), titanium nitride (TiN.sub.x),
tungsten (W), tungsten nitride (WN.sub.x), cobalt, cobalt alloys
such as cobalt-tungsten alloy, cobalt-phosphorus alloy, cobalt-tin
alloys, cobalt-tungsten-phosphorus, cobalt-tungsten-boron, and
combinations thereof. The barrier layer 330 may be deposited by
chemical vapor deposition (CVD), physical vapor deposition (PVD),
electroless deposition techniques, or molecular beam epitaxy among
others. The barrier layer 330 may also be a multi-layered film
deposited individually or sequentially by the same or by a
combination of techniques, such as a tantalum nitride layer
deposited on a tantalum layer, both layers deposited by a physical
vapor deposition technique.
[0084] A seed layer 340 of a metal layer is deposited over the
barrier layer 330 by an electroless deposition process as shown in
FIG. 3C. Suitable seed layer materials include cobalt, cobalt
alloys such as cobalt-tungsten alloy, cobalt-phosphorus alloy,
cobalt-tin alloys, cobalt-tungsten-phosphorus,
cobalt-tungsten-boron, and combinations thereof. The seed layer may
be deposited by first forming or depositing an initiation layer and
then the bulk of the seed layer material.
[0085] For example, the initiation layer may be a noble metal
deposited by an initiation electroless solution comprising between
about 80 ppm and about 300 ppm palladium chloride (PdCl.sub.2) and
sufficient hydrochloric acid (HCl) to produce a pH of between about
1 and about 3. The initiation electroless solution is generally
applied to the substrate surface for between about 5 seconds and
about 60 seconds at a solution temperature between about 20.degree.
C. and about 25.degree. C., or at conditions sufficient to deposit
the initiation layer to a thickness of about 10 .ANG. or less.
[0086] Alternatively, a boride layer may be formed by exposing the
barrier layer to a composition including a borane-containing
reducing agent, for example, about 4 g/L of dimethylamine borane
(DMAB) and sufficient sodium hydroxide to provide a pH of about 9
for the composition, which is applied to the substrate surface for
about 30 seconds at a composition temperature of about 25.degree.
C. The substrate surface is then rinsed with deionized water to
remove any remaining electroless solution or borane-containing
composition.
[0087] Then the bulk of the seed layer material, such as cobalt or
cobalt alloy, is deposited on the initiation layer. The bulk of the
seed layer material is deposited from an electroless technique
using an electroless solution containing a metal salt and a
reducing agent. For example, an electroless solution of between
about 2.5 g/L and about 20 g/L, of cobalt chloride and/or cobalt
sulfate, and between about 15 g/L and about 30 g/L, of sodium
hypophosphite, and sufficient base to provide a pH level of between
about 9 and about 11, may be used. Dimethylamine borane may be used
as the reducing agent at a concentration between about 0.25 g/L and
about 6 g/L. The electroless solution is generally applied to the
substrate surface for between about 5 seconds and about 120 seconds
at a solution temperature between about 20.degree. C. and about
25.degree. C.
[0088] The substrate surface is then cleaned using a cleaning
composition comprising HCl at a pH between about 1 and about 3 for
between about 5 seconds and about 300 seconds at a solution
temperature between about 15.degree. C. and about 80.degree. C.
Ultrasonic energy is applied to the cleaning composition and/or
substrate to improve the cleaning process. The cleaning composition
is generally applied under conditions sufficient to remove about 20
.ANG. or less of the seed layer 340.
[0089] The aperture is then filled by the deposition of a
conductive material 350 into the feature. Conductive materials 350
may include, for example, copper or tungsten. The conductive
material 350, may be deposited by chemical vapor deposition (CVD),
physical vapor deposition (PVD), electrochemical deposition
techniques, such as electroplating, or combinations thereof, with
copper, for example, deposited by an electroplating technique. An
example of a conductive fill of tungsten on a cobalt barrier or
seed layer is more fully described in U.S. patent application Ser.
No. 10/044,412, filed on Jan. 9, 2002, entitled, "Barrier Formation
Using A Novel Sputter Deposition Method", which is incorporated by
reference herein to the extent not inconsistent with the disclosure
or claims herein.
[0090] Following deposition of the material in the aperture, the
filled aperture may be further processed by annealing or
planarizing the top portion of the aperture to form a feature, such
as by chemical mechanical polishing (CMP). During the planarization
process, portions of the one or more dielectric materials 310, the
barrier layer 330, the seed layer 340, and the conductive material
350 are removed from the top of the structure leaving a fully
planar surface leaving exposed conductive material 350 in the
dielectric materials 310.
[0091] Silicide Layer Formation
[0092] A metal silicide layer may be formed by depositing a metal
on a silicon-containing material and annealing the metal and
silicon-containing material to form a metal silicide layer. Metal
silicide is broadly defined herein as an alloy of metal and
silicon, which may exist in multiple valence phases. For example
cobalt and silicon can exist in the CoSi and CoSi.sub.2 phases. The
annealing process to form the metal silicide layer may be performed
in one or more annealing steps and may be performed concurrently
with further deposition processes.
[0093] While the following material describes the formation of a
metal silicide layer from a cobalt or cobalt alloy layer, the
invention contemplates the use of other materials, including
nickel, tin, titanium, tantalum, tungsten, molybdenum, platinum,
iron, niobium, palladium, platinum, and combinations thereof, and
other alloys including nickel cobalt alloys, cobalt tungsten
alloys, cobalt nickel tungsten alloys, doped cobalt and nickel
alloys, or nickel iron alloys, to form the metal silicide material
as described herein.
[0094] One example of a metal silicide application includes the
formation of a MOS device shown in FIG. 4. In the illustrated MOS
structure, conductive N+ source and drain regions 402 and 404 are
formed in a P type silicon substrate 400 adjacent field oxide
portions 406. A gate oxide layer 408 and a polysilicon gate
electrode 410 are formed over silicon substrate 400 in between
source and drain regions 402 and 404 with oxide spacers 412 formed
on the sidewalls of polysilicon gate electrode 410.
[0095] A cobalt layer is deposited over the MOS structure, and in
particular over the exposed silicon surfaces of the conductive
source and drain regions 402 and 404, and the exposed top surface
of polysilicon gate electrode 410 by the process described
herein.
[0096] In one aspect, the cobalt layer may be deposited by the
processes described herein. For example, an initiation layer is
first deposited over the substrate surface and in particular over
the exposed silicon surfaces of the conductive source and drain
regions 402 and 404. The initiation layer (not shown) may include a
noble metal, of which noble metals that form silicides are
typically used. The initiation layer is deposited by an initiation
electroless solution comprising between about 80 ppm and about 300
ppm palladium chloride (PdCl.sub.2) and sufficient hydrochloric
acid (HCl) to produce a pH of between about 1 and about 3. The
initiation electroless solution is generally applied to the
substrate surface for between about 5 seconds and about 60 seconds
at a solution temperature between about 20.degree. C. and about
25.degree. C., or at conditions sufficient to deposit the
initiation layer to a thickness of about 10 .ANG. or less.
[0097] Alternatively, a boride layer may be formed by exposing the
silicon-based materials to a composition including a
borane-containing reducing agent, for example, about 4 g/L of
dimethylamine borane (DMAB) and sufficient sodium hydroxide to
provide a pH of about 9 for the composition, which is applied to
the substrate surface for about 30 seconds at a composition
temperature of about 25.degree. C. The substrate surface is then
rinsed with deionized water to remove any remaining electroless
solution or borane-containing composition.
[0098] A metal layer of cobalt or cobalt alloy is then deposited on
the initiation layer. The cobalt layer is deposited from an
electroless technique using an electroless solution containing a
cobalt salt and a reducing agent. For example, an electroless
solution of between about 2.5 g/L and about 20 g/L, of cobalt
chloride and/or cobalt sulfate, and between about 15 g/L and about
30 g/L, of sodium hypophosphite, and sufficient base to provide a
pH level of between about 9 and about 11, may be used.
Dimethylamine borane may be used as the reducing agent at a
concentration between about 0.25 g/L and about 6 g/L. The
electroless solution is generally applied to the substrate surface
for between about 5 seconds and about 120 seconds at a solution
temperature between about 20.degree. C. and about 25.degree. C. The
substrate surface may then be cleaned prior to subsequent
processing
[0099] The cobalt material is deposited to a thickness of about
1000 .ANG. or less for the subsequent reaction with the underlying
silicon at 402 and 404. For example, cobalt may be deposited to a
thickness between about 50 .ANG. and about 500 .ANG. on the silicon
material.
[0100] In one aspect, the cobalt layer is then annealed by a
two-step annealing process to form cobalt silicide. For example, a
two step annealing process is used to convert the metal layer to a
first phase of metal silicide, such as partially or completely
converting cobalt and silicon to a first cobalt silicide (CoSi)
phase, in a first annealing process; and substantially converted
the metal layer to the desired silicide phase, such as such as
converting the first cobalt silicide (CoSi) phase to a cobalt
silicide (CoSi.sub.2) product, in a second annealing step.
[0101] The one or more annealing steps are generally performed at
an annealing temperature between about 300.degree. C. and about
900.degree. C. and may be for a time between about 10 seconds and
about 600 seconds each. For example, the substrate may be heated to
a temperature between about 400.degree. C. and about 600.degree. C.
for between about 5 seconds and about 300 seconds, such as about
500.degree. C. for between about 60 seconds and about 120 seconds,
and then heated to a temperature between about 600.degree. C. and
about 900.degree. C. for a period of time between about 5 seconds
and about 300 seconds to form the metal silicide layer, such as at
800.degree. C. for between about 60 seconds and 120 seconds.
[0102] The first annealing step may be performed immediately after
deposition of the cobalt layer. The second annealing step may be
performed before, after, or during deposition of subsequent
materials, such as during a chemical vapor deposition of a tungsten
fill layer. The second annealing process generally has a higher
annealing temperature than the first annealing process.
[0103] Two step annealing process for forming metal suicides are
more fully described in U.S. patent application Ser. No.
09/916,234, filed on Jul. 25, 2001, entitled, "In-Situ Annealing
Process In Physical Vapor Deposition System", and U.S. patent
application Ser. No. 10/044,412, filed on Jan. 9, 2002, entitled,
"Barrier Formation Using A Novel Sputter Deposition Method", which
are incorporated by reference herein to the extent not inconsistent
with the disclosure or claims herein.
[0104] Dielectric materials 422 may be deposited over the formed
structure and etched to provide contact definitions 420 in the
device. The contact definitions may then be filled with a contact
material, such as tungsten, aluminum, or copper, from chemical
vapor deposition techniques, such as described herein.
[0105] In one aspect, any unreacted cobalt from the annealing
processes may be removed from the substrate surface, typically by a
wet etch process or plasma etch process, and the cobalt silicide
remains as cobalt silicide (CoSi.sub.2) portions 414, 416, and 418
of uniform thickness respectively formed over polysilicon gate
electrode 410 and over source and drain regions 402 and 404 in
silicon substrate 400. Unreacted cobalt may be removed by a plasma
process in a DPS.TM. chamber located on the same vacuum processing
system, or may be transferred to another processing system for
processing. Wet etch process are typically performed in a second
processing system.
[0106] A selective etch of the unreacted metal layer from the metal
silicide layer may be performed concurrently or after annealing.
Additional deposition of materials, such as a layer of barrier
material or the second metal layer, may be performed concurrently
or after annealing.
[0107] While not shown, a barrier or liner layer of a material,
such as titanium nitride, may be deposited on the cobalt material
to further enhance the barrier properties of the cobalt layer. The
deposition of the titanium nitride layer may replace the step of
removing unreacted cobalt as described above. However, the
unreacted cobalt and titanium may be removed by the etch process
after annealing of the substrate surface according to the anneal
processes described herein.
[0108] While the foregoing is directed to embodiments of the
present invention, other and further embodiments of the invention
may be devised without departing from the basic scope thereof, and
the scope thereof is determined by the claims that follow.
* * * * *